A mathematical model for analysis of pharmacologically induced changes in the kinetics of cardiac muscle

A mathematical model of the isometric contraction of cardiac muscle is developed and utilized to characterize the inotropic and lusitropic effects of cardioactive compounds in isolated guinea pig left atria. In contrast to metrics that are based on minima and maxima of an isometric twitch and its derivative function, the entire time course of the twitch is used to quantify the kinetics of the contraction-relaxation cycle. The model relates observed tension to a time-dependent activation function that describes generation of internal force and a coupling function that determines mechanical response to the activation function. The model is structured so that it is suitable for nonlinear curve fitting to observed data. Results obtained using the model for fitting experimental data from tissues treated with different classes of cardioactive compounds agree with more qualitative results presented by other authors. Experiments using the model to fit data over an extended (90 min) time course revealed differences in the kinetic profiles of milrinone and forskolin. Computer simulations that demonstrate the effect of each model parameter on twitch kinetics are presented, and the relationships between the model and other theoretical and empirical models of cardiac muscle are discussed. The mathematical model is useful to enable a more quantitative understanding of the kinetics of cardiac muscle contraction and relaxation and identify compounds that may be selective for inotropic or lusitropic effects.

Novel mouse embryonic renal marker gene products differentially expressed during kidney development

Investigators approaching the problem of renal organogenesis have been hampered by a paucity of suitable molecular markers that specify distinct developmental phenotypes. To identify such markers, differential display-polymerase chain reaction (DD-PCR) was used to survey the temporal pattern of gene expression in mouse kidney at 11.5, 13.5, 15.5, and 17.5 days after conception and in the adult kidney. Twenty-two differentially expressed amplification products were identified, isolated, and sequenced. Seventeen clones showed no significant similarity with previously reported nucleotide sequences: two were similar to two housekeeping gene products, and three were similar to human or rat expressed sequence tags. To confirm the differential expression patterns observed by DD-PCR, semiquantitative reverse transcription-PCR was performed using sequence-specific oligonucleotide primers. Nineteen of 22 clones were differentially expressed during kidney development [mouse embryonic renal marker (MERM) sequences 1-19]. The value of MERMs as developmental markers was further assessed in mouse metanephric organ culture, where the pattern of MERM transcript expression mimicked that observed in vivo. Therefore, the DD-PCR method permitted development of a panel of marker sequences that can be used to characterize renal developmental processes and that may allow the identification of novel, functionally relevant gene products.

Perceptual learning of stereoacuity

It has often been noted that with repeated exposure to random-dot stereograms the time required to perceived depth decreases. Further, with extensive practice, stereoacuity thresholds have been shown to decrease. For both types of learning some researchers have reported specificity of the improvements to retinal location, and have thus suggested that the learning may be localised at early levels of visual processing, such as in primary visual cortex. However, these studies have not adequately ruled out the possibility that the specificity shown may be due to the operation of selective-spatial-attention mechanisms. In the present study this possibility was examined by training observers to judge the relative depth of a pair of stereograms presented equally often in two spatial locations, but stimuli were only presented with one direction of disparity (ie crossed or uncrossed) in any one location. Results indicated that, as expected, observers' judgements improved with practice. However, this improvement transferred completely to stimuli presented with the other direction of disparity in each location. Thus, it is argued that previous findings of retinal-location-specific improvements in stereoacuity may well be due to selective-spatial-attention mechanisms, rather than to learning localised at an early level of visual processing.

Central effects of 5-HT on activity of respiratory and hypoglossally innervated muscles in newborn kittens

1. In decerebrate kittens (n = 29), electrical activity was studied in the 3rd intercartilaginous (inspiratory), the 9th internal intercostal (expiratory) and the hypoglossally innervated muscles (geniohyoid m. and sternohyoid m.) evoked by the application of 5-HT (n = 16) or related agents (5-HT1A agonist, 8-OH-DPAT (n = 6) and 5-HT2 agonist, DOI floor of the IVth ventricle. 2. The application of a control solution (n = 2) produced no significant changes either in minute inspiratory frequency (Fi) or in the electrical activity of the muscles studied. Except for these controls, only one trial with one dose of one drug was performed in a given kitten. 3. A dose-related decrease in Fi was observed in response to 5-HT. Low doses (50-500 nmol, n1 = 8) induced a long-lasting bradypnoea; high doses (5000-10,000 nmol, n2 = 8) induced prolonged periods of apnoea. 4. The apnoeas observed in tracheotomized (n = 3) or non-tracheotomized (n2 = 8) kittens were mainly of central origin and linked to the lengthening of expiratory time. The expiratory muscle activation came on with the reinforcement of the activity of hypoglossally innervated muscles. 5. Application of agonists showed that both the 5-HT-dependent modulation of Fi and the effects of 5-HT on the activity of the muscles studied resulted predominantly from activation of 5-HT2 receptors.

The effect of thrombus on the vascular endothelium of arterialized vein grafts

BACKGROUND

It is known that vein grafts can be salvaged by clot removal, but patency rates are diminished. This study was designed to determine the effects of thrombus on vascular endothelium and the ability of the endothelium to recover normal function.

METHODS

Thirty external jugular vein grafts were placed as bilateral femoral artery interposition grafts in 15 mongrel dogs and allowed to arterialize for a period of at least 12 weeks. Six control grafts were not exposed to thrombus (C-NT). Six other control grafts were exposed to thrombus for 7 days and removed, ie, allowed no in vivo recovery (C-T). The remaining 18 grafts in 9 canines were exposed to autologous thrombus for 5 days and then flow was restored. The right femoral graft was removed 7 days after thrombectomy and the left removed 30 days after thrombectomy. At the time of removal, the grafts were perfused with a balanced salt solution alone and then with arachidonic acid added to the same volume of the salt solution. Perfusates were collected at 5, 15, and 30 minutes. These perfusates were assayed for the presence of 6-keto-prosglandin F1 alpha (6-keto-PGF1(1 alpha)), a metabolite of prostacyclin (PGI2). Over the 30-day recovery period, the amounts of 6-keto-PGF1(1 alpha) produced with and without arachidonic acid added were compared to assess endothelial response. Electron micrographs of the endothelium of all vein grafts were compared to the assay findings.

RESULTS

When arachidonic acid was added to the perfusion system, there was a several fold increase in the production of 6-keto-PGF1(1 alpha) over baseline in all grafts allowed recovery. Grafts (C-T) that were allowed no in vivo recovery had no response to arachidonic acid. Ratios of 6-keto-PGF1(1 alpha) production with arachidonic acid stimulation to 6-keto-PGF1(1 alpha) production without stimulation were calculated to compare endothelial function. The electron micrographs showed the vascular endothelium to be severely injured after contact with thrombus, but recovered by 7 days.

CONCLUSIONS

This study suggests that the endothelium of canine vein grafts is injured by contact with thrombus for 5 days but can recover structure and function. This recovery is detectable at 7 days post-thrombectomy.

[Iodine-125-brachytherapy of malignant choroid melanoma. II: Long-term functional outcome]

BACKGROUND

Following I-125 brachytherapy of choroidal melanoma, a good primary postoperative visual acuity results. The aim of this study is to evaluate postoperative, longterm visual acuity answering the following questions: 1) When do radiogenic complications begin to develop; 2) How long does the postoperative visual acuity remain stable; 3) Is there a difference if the treated tumor is < or = or > 3 mm off the disc and foveola respectively.

PATIENTS AND METHODS

Between 12/1984-12/1989, 19 patients were treated with I-125 brachytherapy for choroidal melanoma. Height of tumor was x 5.8 mm, maximum base diameter x 11.6 mm. In 10 eyes (group A), the posterior tumor border was < or = 3 mm off the disc and foveola respectively, in 9 (group B) > 3 mm. The plaque was in situ x 7.5 days, apical radiation dose x 70 Gy, and scleral contact dose x 355 Gy. Follow-up ranged at x 6.3 years.

RESULTS

Between preoperative visual acuity in group A and group B there was a statistically significant difference (p < 0.05), which remained stable 1 1/2 years postoperatively. Subsequent deterioration of visual acuity occurred later in group B than in group A, but was present after 4 1/2 years in all patients and ranged at < or = 20/400. This decrease was due to subsequent radiogenic oculopathy.

CONCLUSIONS

Radiogenic complications following I-125 brachytherapy begin within the first 6 months. In group B visual acuity deteriorated later, but after 4 1/2 years, it decreased due to radiogenic oculopathy to 20/400 in all patients. Prospective longterm studies are needed to evaluate whether I-125 should be indicated for larger melanomas and Ruthenium-106 for smaller melanomas to obtain better longterm visual results.

[Exploratory study of amitriptyline resistance in depressed patients: results of WHO French collaborating center on depressions resistant to treatments]

A multicountry, multicentre double-blind study in a group of depressives, coordinated by the Mental Health Division of the World Health Association (WHO) has been done. The goal of the study is to determine whether the therapeutic effects of amitriptyline can be enhanced and potentiated by combining it with an antioxydant (gingko biloba). An exploratory study has preceded the main study which had the objective to estimate the proportion of non-response patient to amitriptyline. We report the results concerning the French center. 23 inpatients meet the ICD-10 criteria for depression (F32 and F33) and were treated during 6 weeks by amitriptyline with the initial daily dose of 50 mg until the maximum dose of 200 mg. The proportion of non-responsive patient to amitriptyline was 34.78 (95% confidence interval : 15.32 to 54.24%), all clinically deteriorated.

Radiographic features of staphylococcal pneumonia in adults and children

BACKGROUND

Clinical and laboratory features do not accurately correlate with the cause of community acquired pneumonia. A study was performed to examine whether the radiographic features of staphylococcal pneumonia are sufficiently distinct to aid early diagnosis.

METHODS

The chest radiographs of 34 patients (including eight children) with proven staphylococcal pneumonia were reviewed by two experienced observers using methods described previously. Features on presentation and follow up were noted.

RESULTS

The most striking features were the presence of multilobar consolidation on presentation, cavitation, pneumatocoeles and spontaneous pneumothorax, together with a tendency to radiographic deterioration after admission in both adults and children. Some of these features are much less common with other causes of community acquired pneumonia. However, most of the cases did not have these classic features.

CONCLUSIONS

The presence of certain radiographic features, including multilobar shadowing, cavitation, pneumatocoeles, and spontaneous pneumothorax, are seen with staphylococcal pneumonia in adults and children, but their absence does not exclude the diagnosis.

The quality of hospital discharge: a survey of discharge arrangements for the over-65s

A three-phase study comprising semi-structured interviews with patients and/or their carers, follow-up postal questionnaires, and a postal survey of the views of professionals involved in the discharge of participating patients was conducted to assess the quality of arrangements for patients over 65 years of age, discharged from hospitals in Chester and Ellesmere Port in the United Kingdom. A large majority of patients (80%) felt they had been adequately consulted about arrangements for their discharge, but less than 2% of health and social care professionals considered all discharges satisfactory. This apparent disparity between patient and professional views may be explained by low levels of expectation among patients in this aspect of their care and their reluctance to express views which they fear may compromise future care. Continuing difficulties with interprofessional communication and liaison suggest that further attention to discharge management is required if improvements are to be effected.

Environmental tobacco smoke exposure and health effects in children: results from the 1991 National Health Interview Survey

OBJECTIVE

To determine the effect of environmental tobacco smoke exposure on the health of children in the United States.

DESIGN AND SETTING

Cross-sectional study of children who participated in the 1991 National Health Interview Survey.

PARTICIPANTS

17448 children residing in the United States.

MAIN OUTCOME MEASURES

Rates of respiratory illnesses and all illnesses, and the morbidity due to these illnesses, in children exposed to environmental tobacco smoke in the home daily compared with those in children not exposed in the home. Our analyses controlled for age, socioeconomic status, race, family size, sex, season, and region of the country.

RESULTS

Children who were exposed to environmental tobacco smoke had a higher incidence of acute respiratory illnesses (relative risk (RR) = 1.10, 95% confidence interval (CI) 0.95 to 1.26) and all chronic respiratory diseases (RR = 1.28, 95% CI 0.99 to 1.65) than children who were not exposed, although both CIs included unity, and chance cannot be ruled out as being responsible for these findings. Children who were exposed to environmental tobacco smoke had, on average, 1.87 more days of restricted activity (95% CI 0.20 to 3.54), 1.06 more days of bed confinement (95% CI 0.20 to 1.92), and 1.45 more days of school absence (95% CI 0.40 to 2.50) per year than children who were not exposed.

CONCLUSIONS

Environmental tobacco smoke exposure in the home, which is completely preventable, is an important predictor of increased morbidity in children.

Immediate and reversible platelet inhibition after intravenous administration of a peptide glycoprotein IIb/IIIa inhibitor during percutaneous coronary intervention

We studied the pharmacokinetic and pharmacodynamic properties of integrelin, a novel platelet glycoprotein IIb/IIIa receptor inhibitor, in patients undergoing elective percutaneous coronary intervention. Patients were randomized to placebo (n = 19) or to 1 of 4 integrelin dosing regimens (total n = 54) that were studied sequentially. All patients received aspirin and heparin. Patients were followed until discharge for the occurrence of adverse clinical events: death, myocardial infarction, coronary artery bypass surgery, repeat intervention, or recurrent ischemia. Bleeding was the primary safety end point. Frequent blood sampling was performed for adenosine diphosphate-induced platelet aggregations. Simplate bleeding times were performed. Adverse clinical events occurred less often in the integrelin-treated patients, although the overall numbers were too small to make a definitive statement as to clinical efficacy. There was no significant increase in serious bleeding among integrelin-treated patients. The 2 highest integrelin boluses (180 and 135 micrograms/kg) immediately (15 minutes after the bolus) provided > 80% inhibition of adenosine diphosphate-induced platelet aggregation in > 75% of treated patients. A constant integrelin infusion of 0.75 micrograms/kg/min maintained this marked antiplatelet effect, whereas an infusion of 0.50 micrograms/kg/min allowed gradual recovery of platelet function. Elective coronary intervention was performed safely and with no significant increase in serious bleeding events using integrelin with aspirin and heparin as an antithrombotic regimen. Integrelin provided rapid, intense, and persistent ex vivo platelet inhibition during coronary intervention. This new antiplatelet agent may be beneficial in reducing platelet-mediated ischemic complications of percutaneous coronary intervention.

Randomized Trial of the Canalith Repositioning Procedure

Thirty-six subjects with confirmed, unilateral benign paroxysmal positioning vertigo of at least 2 months' duration were randomly assigned to one of two treatment groups. After complete informational counseling and explanation of the posttreatment instructions, subjects were randomly assigned to receive either Epley's canalith repositioning procedure or a placebo maneuver. All subjects completed a daily diary for 1 month to document any dizzy spells and their adherence to the posttreatment instructions. Follow-up Dix-Hallpike testing was performed after 1 month by an audiologist who was blinded to the patient's treatment group status. Analysis of Dix-Hallpike results confirmed that those who received the canalith repositioning procedure had significantly more negative responses (88.9%) than did those in the placebo group (26.7%).

Design and Development of An Artificial Neural Network for Estimation of Formation Permeability

Abstract

Permeability is one of the most important characteristics of hydrocarbon bearing formations. An accurate knowledge of permeability gives petroleum engineers a tool for efficiently managing the production process of a field. It is also one of the most important pieces of information in the design and management of enhanced recovery operations. Formation permeability is often measured in the laboratory from cores or evaluated from well test data. Core analysis and well test data, however, are only available from a few wells in afield. On the other hand, almost all wells are logged.

In this study an artificial neural network has been designed that is able to predict the permeability of the formations using the data provided by geophysical well logs with good accuracy. Artificial neural network, a biologically inspired computing method, with its ability to learn, self-adjust, and be trained provide a powerful tool to solve problems that involve pattern recognition.

Using well logs to predict permeability has been attempted in the past. The problems with previous approaches were mainly two fold, namely, the number of variables used (only one variable-porosity), and using regression analysis as the main tool for correlations. The approach introduced in this paper is an attempt to overcome these short comings. This is done, first, by using many variables from well logs that may provide information about the permeability. Second, by recognizing the existence of possible patterns between these variables and formation permeability using artificial neural networks. Neuralnets are analog, inherently parallel and distributive systems. These characteristics, which will be discussed in the paper, are the main characteristics that enable artificial neural networks to be successful in predicting the permeability in rocks using well log information.

Introduction

Acquiring knowledge on formation permeability has remained one of the fundamental challenges to petroleum engineers.

Randomized trial of the canalith repositioning procedure

Thirty-six subjects with confirmed, unilateral benign paroxysmal positioning vertigo of at least 2 months' duration were randomly assigned to one of two treatment groups. After complete informational counseling and explanation of the posttreatment instructions, subjects were randomly assigned to receive either Epley's canalith repositioning procedure or a placebo maneuver. All subjects completed a daily diary for 1 month to document any dizzy spells and their adherence to the posttreatment instructions. Follow-up Dix-Hallpike testing was performed after 1 month by an audiologist who was blinded to the patient's treatment group status. Analysis of Dix-Hallpike results confirmed that those who received the canalith repositioning procedure had significantly more negative responses (88.9%) than did those in the placebo group (26.7%).

Activity of lytic peptides against intracellular Trypanosoma cruzi amastigotes in vitro and parasitemias in mice

Three cecropin-like lytic peptides (DC-1, DC-2, and DC-2R) were synthesized with virtually no sequence homology with the natural compound (cecropin B) while retaining the charge distribution, amphipathic, and hydrophobic properties of the natural compound. A fourth analog (alpha-Pi) without these later properties, but a similar molecular weight, was also synthesized as a nonlytic peptide control. The 3 lytic peptides were examined for their ability to kill Trypanosoma cruzi trypomastigotes in vitro, intracellular amastigotes in vitro, and their toxicity to a mammalian cell line. DC-2 at 5 microM and DC-1 and DC-2R at 10 microM were 100% effective in killing T. cruzi trypomastigotes in vitro, suggesting at least a 10-fold increase in lytic activity over previous tested lytic peptide analogues, SB-37 and Shiva-1. When T. cruzi-infected Vero cells were treated with a single or double exposure of low concentrations (2.5 microM) of DC-1, DC-2, and DC-2R there was a significant (P < 0.05) reduction in amastigote numbers/cell when compared to untreated and alpha-Pi-treated T. cruzi-infected cells. Vero cells alone treated with the lytic peptides showed no reduction in number or toxicity. One of the peptides (DC-1) was tested for its toxicity in AJ mice and its ability to reduce parasitemias in T. cruzi-infected AJ mice. No untoward effects were seen in AJ mice injected intravenously with 50 micrograms/mouse daily for 10 days. There was a significant (P < 0.05) reduction in parasitemia and mortality by day 14 postinoculation (from 100% to 0%) in T. cruzi-infected AJ mice given 25 micrograms of DC-1/mouse on days 2, 4, 6, 8, and 10 postinoculation.

Design and synthesis of conformationally constrained analogues of 4-(3-butoxy-4-methoxybenzyl)imidazolidin-2-one (Ro 20-1724) as potent inhibitors of cAMP-specific phosphodiesterase

The synthesis and biological evaluation of cAMP-specific phosphodiesterase (PDE IV) inhibitors is described. The PDE IV inhibitor 4-(3-butoxy-4-methoxybenzyl)imidazolidin-2-one (Ro 20-1724, 2) was used as a template from which to design a set of rigid oxazolidinones, imidazolidinones, and pyrrolizidinones that mimic Ro 20-1724 but differ in the orientation of the carbonyl group. The endo isomer of each of these heterocycles was more potent than the exo isomer in an enzyme inhibition assay and a cellular assay, which measured TNF alpha secretion from activated human peripheral blood monocytes (HPBM). Imidazolidinone 4a inhibited human PDE IV with a Ki of 27 nM and TNF alpha secretion from HPBM with an IC50 of 290 nM. By comparison, Ro 20-1724 is significantly less active in these assays with activities of 1930 and 1800nM, respectively.

Duration illusions in a train of visual stimuli

The first stimulus in a sequential train of identical flashes of light appears to last longer than those in the middle of the train. Four flashes (each 600 or 667 ms) were presented and the first was shortened until it appeared to have the same duration as that of the next. The duration of the first stimulus was found to be overestimated by about 50%. The illusion was unaffected by stimulus contrast, size, or interflash interval (between 100 and 600 ms). For some subjects, the last stimulus in the train also appeared to be about 50% longer than the penultimate flash. The results are discussed in terms of theories of how attention, arousal, and stimulus processing can affect duration perception. The mechanisms activated are peculiar to the visual system, since no similar illusion of duration was consistently experienced with a train of auditory tones.

Central effects of 5-HT on respiratory and hypoglossal activities in the adult cat

The activities of the diaphragmatic, internal intercostal and hypoglossal-innervated muscles were studied in adult decerebrate cats in response to 5-HT and related agents (8-OH-DPAT and DOI). The drugs were placed on the floor of the IVth ventricle. The mean respiratory frequency (Fi) increased (124-193% of the control value) within 3 min of the 5-HT application, and decreased thereafter (30-90%). The mean Ti and Te changed similarly, but opposite to Fi. With some delay, the hypoglossal-innervated muscles were tonically activated or exhibited increased activities. Methysergide pretreatment completely blocked the effect of 5-HT on all the respiratory parameters and the hypoglossal-innervated muscles activities. The responses to 8-OH-DPAT and DOI indicate that 5-HT modulates the respiratory frequency via activation of both 5-HT1A and 5-HT2 receptors. Nevertheless, the effect of 5-HT on both the expiratory and hypoglossal-innervated muscles seems to depend on 5-HT2 receptors activation only.

Resistance of HIV type 1 to proteinase inhibitor Ro 31-8959

During replication of human immunodeficiency virus type 1 (HIV-1), proteolytic cleavage of Gag and Gag-Pol precursor proteins into different functional protein subunits is catalyzed by the viral proteinase, and this enzyme is the target of the antiviral proteinase inhibitor, Ro 31-8959. We investigated in vitro which HIV mutants with reduced sensitivity to Ro 31-8959 emerged during proteinase inhibition treatment; from three different HIV-1 strains, comparable progeny virus resistant to proteinase inhibitor were found, whereas the same experimental protocol detected no resistant HIV-2 mutants. Molecular analysis of the mutations underlying resistance revealed a multistep mechanism in which an amino acid exchange was common to all resistant isolates, and in all experiments preceded further exchanges at position 90 (leucine to methionine) and/or at position 54 (isoleucine to valine). For wild-type strains the 90% inhibitory concentrations of Ro 31-8959 were close to 20 nM, whereas HIV-1 mutants with all 3 amino acid exchanges had more than 50-fold increased 90% inhibitory concentrations (above 1000 nM). The primary event (Gly-48 to valine) occurs at the hinge of the flaps of the proteinase, thus hampering entry of the inhibitor to the active center and suggesting steric hindrance. Detailed knowledge of this stereotypic process could open inhibitor design, thus preventing conceivable escape of resistant virus on proteinase inhibitor action.